Inhibitor for gasoline



Reiuued June 1950 INHIBITOR FOR GASOLINE Robert H. Rcsenwald, WesternSprings, and Joseph A. Ohenicek, Bensenville, Ill., assignors toUniversal Oil Products Company,

Chicago,

111., a corporation of Delaware No Drawing. Original No. 2,310,710,dated February 9, 1943, Serial No. 295,476, September 18, 1939.Application for reissue December 7, 1948,

Serial No. 64,028

19 Claims.

Matter enclosed in heavy brackets reissue specification; matter printedin This invention relates to a method for stabilizing olefin-containinghydrocarbon oils, and more particularly, cracked gasolines of thepetroleum origin. However, gasolines from other sources, such as coaltar, shale oil, etc., may be also treated according to the presentinvention, as may those made by polymerization of olefins, reforming ofnaphthas, etc.

More specifically, the invention concerns a method for stabilizingolefin-containing gasolines during storage in respect to their valuableproperties such as color and anti-knock value and low gum content whichtend to depreciate because of the action of oxygen upon the olefins insaid gasollnes.

The cracking and reforming processes which are employed to produceadditional yields of gasoline from heavy hydrocarbonaceous oils, or toincrease the anti-knock properties of naphthas and straight rungasolines, produce motor fuels having substantial concentrations ofunsaturated hydrocarbons. particularly mono-olefins and diolefins. Theseolefinic hydrocarbons tend to form peroxides and gums when stored in thepresence of oxygen. The use of inhibitors to prevent such reactions hasbeen practiced, and many types of compounds have been suggested for thispurpose, including aminophenols, wood tar fractions, polyhydroxyphenols, etc.

In one specific embodiment, the present invention comprises thetreatment of unstable olefincontaining gasolines to preserve theirvaluable properties in respect to gum content, color and anti-knockvalue by adding thereto minor quantitles of 2-alkyl-i-alkoxyphenols ofthe general structure wherein R comprises any alkyl group and OR is analkoxy group wherein R is of the same or different molecular weight andstructure than R.

The properties desirable in a gasoline gum inhibitor are as follows:

[ appears in the original patent but forms no part of this italicsindicates the additions made by reissue a. Solubility in the gasoline toa degree in excess of the maximum concentration in which it is likely tobe used.

b. High degree of potency so that relatively small concentrations can beused.

c. Insolubility or relatively low solubility in water or aqueousalkaline or acidic solutions with which the gasoline is likely to comein contact.

d. Either normally liquid or having a high degree of solubility in anon-aqueous, gasolinemiscible solvent thus increasing the ease ofhandling and addition to thegasoline.

e. Non-reactive with tanks, fittings, lines, engine parts, etc, withwhich the gasoline is likely to come in contact.

1. Of light color, and imparting or developing no objectionable color orodor to the gasoline when added, or during storage.

The inhibitors of the present invention too. large extent fulfil theserequirements.

The degree of insolubility of an inhibitor in water or caustic solutionsis of particular importance since gasoline storage tanks generallycontain water which is alkaline in reaction. Ii the inhibitor is solublein the water layer, it is partially removed from the gasoline and thusits effect is greatly reduced. The present type of compound has beenfound to be practically insoluble in water and in most cases to be butslightly removable from gasoline by contact with dilute alkalinesolutions.

The compounds of the present invention are useful for preventing thedeterioration of gasoline, but different individual compounds of thesame type are not necessarily exact equivalents.

The alkyl groups substituted in the ring may comprise any alkyl groupsuch as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondarybutyl, t-butyl, amyl, isoamyl, secondary amyl, etc. 01'

these groups the t-alkyl groups appear to be more effective incontributing to the inhibitor potency of the resultant compound than dothose groups of lower molecular weight, for example methyl and ethylgroups. Likewise, the groups of higher molecular weight contribute toother desirable properties of the inhibitor such as decreasing thesolubility of the resulting compound in aqueous solutions. Thesubstituent group is preferably in the position ortho to the hydroxylgroup.

aaasa Some compounds having alkyl groups in the meta position may alsohave inhibiting value.

We have found that when the alkoxy or ether group is in the 4-position,compounds having greater inhibitor potency are available than when thisgroup is in any other position in the substituted phenol. The alkylgroup oi this alkoxy substituent may comprise for example ethyl. methyl,propyl, isopropyl, butyl, isobutyi, secondary butyl, t-butyl, amyl,isoamyl, secondary amyl. t-amyl, etc. groups. Oi these, the groups orrelatively low molecular weight, comprising methyl or ethyl groupsappear to have the strongest influence, although other groups haveconsiderable value. Straight-chain alkyl substituents or greater lengththan two carbon atoms tend to produce inhibitors of lower potencies thanwhen methyl or ethyl groups are substituted. An example of the improvedeii'ectiveness of the present type of inhibitor is illustrated as fol- Br uinone Hvdwim mmrl ether-1.69 noQon mco- :?on

:HI iHl i-ethylhydroquinone fl-ethyl-Mnethoxyphenol potency as comparedwith a widely used commercial gum inhibitor. From the illustration itquinone have little or no inhibitor value compared with the commercialinhibitor. The monomethyl ether of hydroquinone has a considerablepotency, being 1.69 times as eflective as the commercial inhibitor. Thesubstitution of an ethyl group in the position ortho to the hydroxylgroup (2- ethyl-4-methoxyphenol) increases the inhibitor ratio to aneven greater extent, so that the resulting 2-ethyl-4-methoxyphenol is2.39 times as eii'ective as the commercial inhibitor.

The alkyl substituents may be introduced into the aromatic nucleus in anumber of ways. One oi these consists in alkylating a hydroq'uinoneether by contacting it at a temperature 01' -80" C. with the alcoholcorresponding to the group to be substituted, using phosphoric acid asthe catalyst. The reaction mixture is stirred continuously until thereaction is complete. The mixture is then washed with water to removeremaining acid and is extracted with 10% sodium hydroxide solution toremove the unreacted hydroquinone ether. The insoluble portion isdistilled under reduced pressure and the resulting compound may befurther purified by recrystallization.

The term stabilizing" gasoline as used herein is intended to mean theprevention of deterioration of the gasoline in-so-i'ar as its desirableproperties of storage stability, color, anti-knock value, etc., areconcerned.

The following example still further illustrates the benefits andusefulness of the present type of inhibitor. This example is given todemonstrate the usefulness and practicability of our invention, butshould not be construed as limiting it to the exact compoundsillustrated therein. As in the foregoing, the inhibiting value inso-i'aras the stabilization of gasoline is concerned is reported in terms 01'inhibitor ratio compared with a commercially used gum inhibitor.

In the following table are shown a number of representative compounds01' the present invention together with their inhibitor ratios:

TABLEI Irrmrros Rs'rros or 2-Anm-4-Arxommons nr 0.05% Concsmsrron Theresults show that the compounds listed are specially eflectlveinhibitors as compared to a commercial gum inhibitor when used in equal2 weights. They are not, however, exactly equivalent since the specificefiects of different groups in the alkoxy or in the ortho ringsubstituted positions may be quite different. Thus it will be seen thatan ethyl or methyl group in the alkoxy group is more effective thanother alkyl groups 'tried. On the other hand, the substitution of at-butyl group in the aromatic ring greatly increases the inhibitorpotency of the resultant 'noted also that the t-butyl group as the ringsubstituent reduces the alkali solubility oi the compounds to a greaterextent than does an ethyl group in the same position. It will also beobserved that the compounds of the present invention have practically nodetrimental effect on the color or color stability of the gasoline whenadded in these quantities. In all cases, the color 01 the resultinggasoline was equal to or better than that oi. the gasoline inhibitedwith a commercial inhibitor.

It has been our observation in the laboratory The inhibitor potency asmeasured by the oxygen bomb induction period and copper dish gum bothbefore and after washing the inhibited gasoline with water and 5%--byvolume of 1% sodium hydroxide solution is illustrated. In this case thegasoline was inhibited with a sufflcient quantity of each inhibitor toproduce approximately the same induction period. Hydroquinonemonoethylether and monoiso-propylether are included in the list forpurposes of comparison. The percentage of inhibitor removed by water orcaustic is calculated from the per cent decrease in induction periodafter the sample has been washed with water or with caustic solution. Itwill be noted that the compounds of the present invention are lesssoluble in water thanthe commercial inhibitor or hydroquinonemonoethylether. Moreover, these compounds are less soluble in dilutecaustic solution than the monoalkylethers or the commercial guminhibitor. It will be compound. that the inhibitors of this inventionare compara- The efiectiveness is further illustrated by the tivelystable insofar as color is concerned when data presented in Table II.exposed to air. One 01' the disadvantages of many TABLE II Oxygen BombInduction Per Cent Ra- MgCu Dish Gum Period moved Inhibitor ofl WaterCaustic Ori Water Caustic Water Caustic 5 Wash Wash Wash Wash Wash WashBlank gasoline 127 138 134 80 75 Commercial inhibitor 4 24 180 310 26018 89 2-tert-butyl-4-methoxyphen 8 7 9 305 310 295 D 02-tort-butyl-4-ethoxyphenol- 7 9 10 310 335 330 0 0 2-tert-butyl-4-1soropoxy henol 15 15 17 290 295 280 0 0 Z-tert-butyH-iso utoxy enol 16 2419 310 300 295 0 0 2-ethyl-4- inrynhenn 37 64 19 300 300 0 67HthyIA-ethoxy 13 19 28 290 300 0 47 Hydroqu none monoethyl ether 32 38104 310 $0 100 9 89 Hydroqumone mono-isopropyl ether 27 44 115 280 27090 0 92 commercial inhibitors is that they develop color rapidly whenexposed to air. The stable character of the present inhibitors maytherefore be considered an advantage.

We claim as our invention: 7

1. A process for stabilizing olefin-containing hydrocarbon oils inregard to their desirable properties which comprises adding to said 0115a minor portion of a compound having the general structure wherein R andR are alkyl groups.

2. A process for stabilizing olefin-containing gasoline in regard to itsvaluable properties which comprises adding to said gasoline a minorportion of a compound having the general structure wherein R and Rcomprise alkyl groups.

3. A process for stabilizing cracked gasoline against deterioration ofits valuable properties which comprises adding to said gasoline a minorportion of a compound of the following general formula:

wherein R is a t-alkyl group and R is an alkyl group.

4. A process for stabilizing olefin-containing gasoline againstdeterioration of its valuable properties which comprises adding to saidgasoline a minor portion of a compound of the following general formula:

wherein R is a t-butyl group and R is an alkyl r up. a a

I 5. A process for stabilizing olefin-containing gasoline againstdeterioration of its valuable properties which comprises adding to saidgasoline a minor portion of a compound of the-following general formula:

wherein R and R' are t-alkyl groups.

6. A process for stabilizing olefin-containing gasoline againstdeterioration of its valuable properties which comprises adding tosaidgasoline a minor portion of a 2-alkyl-4-a1koxyphenol.

[7. An inhibitor for cracked gasoline which comprises essentially acompound having the general formula:

wherein R and R are alkyl groups] [8. An inhibitor for olefin-containinggasoline which comprises essentially a compound having the generalformula:

wherein R is an alkyl group and R is different aikyl mun-II 9. Aninhibitor [for olefin-containing gasoline] which comprises essentially acompound having the general formula:

wherein R comprises a t-alkyl group and R an alkyl group having asmaller number of carbon atoms than said t-alkyl group.

10. An inhibitor for olefin-containing gasoline which comprisesessentially a compound having the general formula:

wherein R is a t-butyl and R is an alkyl group.

11. An inhibitor for olefin-containing gasoline which comprisesessentially a compound having the general formula:

wherein R and R are t-alkyl groups.

[12. An inhibitor for olefin-containing gasoline which'comprisesessentially a compound having the general formula:

wherein R is an alkyl group and R is a t-alkyl r up-II 13. An inhibitorfor olefin-containing gasoline which comprises essentially a compoundhaving the general formula:

wherein R is a t-alkyl group and R is a t-butyl group.

14. Motor fuel comprising olefinic gasoline and a relatively smallamount or a 2-alkyl-4-alkoxyphenol.

15. Motor fuel comprising olefinic gasoline and a relatively smallamount a: a z-t-alkyl-i-alkoxyphenol.

18. Motor fuel comprising oleflnic gasoline and a relatively smallamount or a compound having the general formula:

wherein R is an alkyl group 01' at least 3 carbon atoms and R. is analkyl group 01' less than 3 carbon atoms.

[17. An inhibitor comprising a 2-alkyl-4-alkoxyphenol] [18. An inhibitorcomprising a compound having the general formula wherein R is an alkylgroup oi at least 3 carbon atomsandR' isanalkylgroupoi'lessthan3 carbonatoms] 19. An inhibitor comprising a Z-tertiargaikul-laikoruphenol.

20. An inhibitor comprising Z-tertimbutul-lmethomhenol.

21. An inhibitor comprising Z-tertiarubutul-lethomhenol.

22. Aainhibitor compriging acompouna having the general formula:

wherein R is a tertiarpallcpl group and R is an alkul group of less than3 carbon atoms.

23. An inhibitor comprising a Z-tertiarualkul- 4-alk0xuphenol in whichthe alley! and alkoxy groups each contain not more than 5 carbon atoms.4

24. An inhibitor comprising a compound having the general formula:

wherein R is a tertiarualkul group of not more than 5 carbon atoms and Ris an alley! group of less than 3 carbon atoms.

ROBERT H. ROSENWALD. JOSEPH A. CHENICEK.

REFERENCES man The following references are ol' record in the flle ofthis patent or the original patent:

UNITED STATES PATENTS Number Name Date 1,884,559 Calcott et al. Oct. 25,1932 1,942,827 Mills et al. Jan. 9, 1934 1,987,2 28 Bruson Jan. 8, 1935OTHER REFERENCE oraanische Chemie, 4th edulrstea Beilstein:

:l'. 114;" vol. VI. m M m

